AboutSyed Rizwan Muhammad Rizvi Expertise I can answers questions regarding web based and desktop based programming in VB.Net. Which can include SOAP, XML, Custom Controls, COM Interoperability etc.
Experience Have been working in this specific area for last 2 years previously I was a VB 6 Developer with experties in other languages as well. Total 10 years of programming experience.
Expert: Syed Rizwan Muhammad Rizvi Date: 7/31/2008 Subject: How to make 15 days trial package s/w vb.net 2005
Question May I please know how to make an installation which works for exactly 15 days and then ask to buy it or uninstall it.
My querry is on what basis to calculate 15 days, if it is system date and time it can be changed by the user so how will my project calculate this time limit.
If there is any other clock which canot be manipulated, please let me know how to use it?
Thanks,
jini
Answer Clocks are manipulatable, but the important thing to notice is that you can certain checks placed to make more fool proof:
e.g.
1. if the system's date has gone back the date of installation your software shouldn't run
2. each time the software runs it stores the last run date somewhere so you can check if the date has been changed or not.
Now the only hack remains is to keep the system on the same date forever which can somehow be managed if you apply point no.2 and save timestamp as well. Unless someone is really crazy and freezes the time on computer in which case you most of his other applications won't work.
